@inproceedings{RoudenkoNeermannSchirmeretal.2021, author = {Roudenko, Jewgeni and Neermann, Simone and Schirmer, Julian and Reichenberger, Marcus and Franke, Jorg}, title = {Sintering of digitally printed silver nanoparticle inks on flexible and rigid substrates by NIR- and UVradiation}, publisher = {IEEE}, doi = {10.1109/mid50463.2021.9361627}, pages = {8}, year = {2021}, abstract = {In the research project AVerdi the influence of photonic sintering methods on the resulting electrical conductivity, sintering duration and adhesion of digitally printed silver nanoparticle inks was investigated and compared to convective sintering. Conductor paths with film thicknesses below 1 μm were applied on flexible polymer substrates via inkjet printing. Aerosoljet printing was used to generate thicker lines up to 11 μm on injection molded substrates. Photonic sintering was carried out with near infrared emitters or ultraviolet light emitting diodes. For inkjet printed structures on polyimide a conductivity up to 24 \% relative to bulk silver was achieved after a sintering duration of 2 s and 5 s for the near infrared and the ultraviolet light source, respectively. Oven sintered samples showed an electrical conductivity of 14 \% after 1 h at 200° C. On polyethylene terephthalate a conductivity around 7 \% was achieved after irradiation with near infrared light for 1 s, whereas convectively sintered samples showed a conductivity around 4 \%. All material combinations sintered by the different methods showed good adhesion. The overall results of long-term behavior after thermal-cycling, regarding electrical conductivity and adhesion, show that the photonically sintered structures achieve similar results compared to the reference. The photonically sintered structures generated with the aerosoljet on polyamide 6 achieved conductivity values up to 19 \%, which were comparable to the furnace sintered reference samples. On liquid crystal polymer substrates conductivity values reached up to 35 \% after sintering with ultraviolet light emitting diodes for 60 s. Oven sintered samples showed a conductivity around 25 \% after 1 h at 150° C. The adhesion of the silver nanoparticle ink on liquid crystal polymer and polyamide 6 substrates is better than with the reference samples. The reliability tests show fewer failures with alternative sintered samples. In this study only the results for inkjet printed structures are presented.}, language = {en} } @inproceedings{RoudenkoHaeusslerFrankeetal.2023, author = {Roudenko, Jewgeni and H{\"a}ußler, Felix and Franke, J{\"o}rg and Reichenberger, Marcus}, title = {Digitally printed strain gauges on 3D metallic objects for pressure sensing}, doi = {10.1109/MID59615.2023.10461323}, pages = {8}, year = {2023}, abstract = {In this study digitally printed carbon and silver strain gauges were examined regarding adhesion, topographical properties and their strain sensitivity on aluminum 2D-objects, in the form of tensile test bars and on metallic 3D-objects, in the form of hollow aluminum cylinders. Both sample types were coated with UV-cured dielectric layers via piezo jet printing. All samples showed good adhesion between the dielectric layer and aluminum with removed area values below 1 \%. Piezo jet printed carbon sensing grids of 30μm thickness also showed good adhesion to the dielectric layers after tapetest. Aerosol jet printed silver grids of 2μm thickness required higher sintering temperatures and two printing passes for good cohesion and adhesion to dielectric layers. The sensitivity of carbon samples was 6.71±0.62 and 8.67±0.79 on 2D-objects and 3D-objects, respectively. Therefore, showing an acceptable correlation with 3D-experiments. The sensitivity of silver samples was 1.91±0.23 and 2.10±0.24 on 2D-objects and 3D-objects, respectively. Therefore, showing a good correlation with 3Dexperiments. Due to a high temperature coefficient of resistance of printed silver (0.276 \%/°C), such strain gauges also can be implemented for temperature sensing, because they showed very good response and stability during temperature cycling tests in the range from -40°C to +100°C.}, language = {en} } @article{HuemmerRoudenkoWengeretal.2022, author = {H{\"u}mmer, Michael and Roudenko, Jewgeni and Wenger, Thomas and Reichenberger, Marcus}, title = {Mechanical characterization of solder interconnections on functionalized, copper-containing polymer thick-film pastes for hybrid integration}, series = {Flexible and Printed Electronics}, volume = {7}, journal = {Flexible and Printed Electronics}, number = {3}, publisher = {IOP Publishing}, issn = {2058-8585}, doi = {10.1088/2058-8585/ac8491}, pages = {15}, year = {2022}, abstract = {In this work, on different substrate materials thermally cured polymer thick-film (PTF) pastes are connected to surface mount technology resistors using a SnBiAg solder alloy. The effect of substrate pre-treatment with atmospheric plasma and thermal cycling on the shear strength of these interconnections is investigated, and the shear forces obtained are graded using United States Defense Standard / Military Standard (MIL-STD) 883. In particular, the build-up of solder interconnections on conductive structures made of commercially available copper-containing PTF pastes and their mechanical characterization is novel. As well as the mechanical characterization of conductive structures, made of PTF pastes, on plasma-treated substrates and their grading using the MIL-STD 883. In addition, interconnections with silver-containing conductive structures are realized for comparison. Depending on the interconnection system, component mean shear forces of up to 31 N are achieved. While some systems meet the 1.25× criterion of MIL-STD 883, the majority of the systems investigated do not meet the 1.00× criterion. Hereby, the adhesion between the conductive structure and the substrate usually fails. Plasma pre-treatment shows an adhesion-increasing effect only for a proportion of substrate materials used, as does thermal aging. But thermal loads can also impair the adhesive strength.}, language = {en} } @article{HelbigHerbstRoudenkoetal.2018, author = {Helbig, Uta and Herbst, Kai and Roudenko, Jewgeni and Helbig, Jens and Barton, Bastian and Kolb, Ute}, title = {Carbon-doped titania as a precursor for titanate nanotubes}, series = {Journal of Materials Research}, volume = {33}, journal = {Journal of Materials Research}, number = {9}, publisher = {Springer Science and Business Media LLC}, issn = {0884-2914}, doi = {10.1557/jmr.2018.49}, pages = {1288 -- 1300}, year = {2018}, abstract = {Carbon-doped titania was fabricated via carbothermal treatment in nitrogen-acetylene gas flow and further used as a precursor for multiwalled titanate nanotube (TNT) synthesis via alkaline hydrothermal route. Investigation of the reaction products after hydrothermal treatment of carbon-doped titania using Transmission electron microscopy, X-ray diffraction, and Brunauer-Emmett-Teller method shows the successful formation of TNTs. The presence of carbon was proved although the type of incorporation could not be certified. All samples show approximately the same carbon content before and after hydrothermal treatment. An increasing pretreatment temperature of titania precursor powders yields more secondary products in the nanotube samples, indicating lower reactivity of the titanium oxycarbide phase during hydrothermal treatment. In this study, TNTs with 6 wt\% carbon and with the highest specific surface area of 340 m2/g were formed via hydrothermal treatment of carbon-doped titania precursor powder exposed to 700 °C during carbothermal pretreatment.}, language = {en} }